In this report we present a procedure to fabricate highly transmissive superconducting contacts. A combination of a sulphur passivation of the etchedsemiconductor prior to the deposition of Nb and an annealing step is used. To quantitatively classify the transparency of the contacts, transport measurements of the differential conductance are carried out at 300 mK and compared with a model given by Blonder, Tinkham, and Klapwijk [Phys. Rev. B 25, 4515 (1981)]. The procedure yields almost ideal superconductor-semiconductor contacts. Additionally, a high reproducibility of the contact transparency is achieved. The results are interpreted in terms of diffusion of In in both the niobium and the

Exponential tapering and inhomogeneous current feed were recently proposed as means to improve the performance of a Josephson flux flowoscillator. Extensive numerical results backed up by analysis are presented here that support this claim and demonstrate that exponential tapering reduces the small current instability region and leads to a laminar flow regime where the voltage wave form is periodic giving the oscillator minimal spectral width. Tapering also leads to an increased output power. Since exponential tapering is not expected to increase the difficulty of fabricating a flux flowoscillator, we suggest that this feature should be incorporated in future designs.

Small amounts of Al and Mn were introduced to partly substitute for Fe in polycrystalline Terfenol alloy as Their effects on structure, magnetic properties, magnetostriction, and hardness were studied. X-ray diffraction shows that the studied alloys remain cubic Laves phase. The saturation magnetization increases with Mn content. Curie temperature dramatically decreases with Mn addition and is further lowered due to the Al replacement. A magnetostriction of 1890 ppm at 19 kOe was obtained in the modified alloy Magnetostriction value at low field is distinctly greater, especially when than that of the or the Mn/Al. At 1 kOe, the magnetostriction of the alloy is 250 ppm compared to, 22 ppm in the base alloy. Addition of both Mn and Al improves the maximum value of dynamic strain coefficient and lowers the corresponding field for alloys as compared with the base alloy. When is 1.7 times higher than that of the base alloy, while the corresponding field is 0.562 kOe, 3.1 times lower than that of the base alloy.

The growth of [101] epitaxialfilms of on substrates has been achieved. The structure,nanostructure, and magnetotransport properties are reported and compared to those of the bulk material. The electron diffraction study evidences, at RT, a monoclinic cell with and β≈91°. The monoclinic distortion is assumed to be due to strain effects. At 92 K, a system of extra reflections is observed which implies an incommensurate modulated structure. The component q of the modulation vector along ranges between 0.35 and 0.40. The lattice images show that the modulation is established throughout the whole film. The q value observed in the film is significantly lower than the one of the bulk material. This effect is correlated to strain effects of the substrate, limiting the cell distortion induced by charge ordering. An unusual insulating-ferromagnetic phase is observed with a critical temperature of 240 K, close to the

Three classes of giant magnetoresistance Co(1 nm)/Cu(2.1 nm) multilayers were sputter grown with different microstructures in respect to grain size and interface roughness, depending on deposition conditions. Magnetization and current in-plane giant-magnetoresistance (GMR) isothermal loops reveal an unusually high increase of coercivity from 280 down to 5 K. In addition, a systematic variation was observed in the temperature dependence of the indirect exchange coupling as the Co–Cu layering is modified in the three classes of Co/Cu multilayers. Specifically, the temperature dependence of the saturation (switching) field in the GMR-loops, and the indirect coupling strength, vary as whereas the spin-blocking temperature is found equal to 84(4), 96(11), and 105(10) K for class A, B, and Cmultilayers, respectively. These results indicate that the desirable low hysteresis appears in the GMR loops at room temperature because the spin structure becomes unstable above the obtained due to domain wall fluctuations. Such magnetic fluctuations define a short–range order state above that depends on Co–Cu intermixing and geometric factors of the grains.

Anisotropy fields in excess of 120 kA/m (1500 Oe) have been produced in 3–5-nm-thick polycrystalline films of Co by oblique sputtering of Ta underlayers. The unusually high anisotropy is magnetostatic in origin and is induced by corrugations on the surface of an obliquely sputteredTa underlayer. Cross-sectional transmission electron microscopy reveals 4 nm columnar grains of Ta tilted toward the Ta source and elongated perpendicular to the Ta flux in the film plane. The anisotropy field of the Co film increases with both the underlayer thickness and the angle between the Ta source and the film normal. In spin valve samples, the anisotropy is attenuated by more than an order of magnitude across a 4-nm-thick Cu spacer. Magnetoresistance measurements on a spin valve indicate less than dispersion in hard axis directions, and despite the nanometer-scale roughness of the underlayer there is weak broadening of the ferromagnetic resonance line.

bulk cylinders and ribbons were quenched from the melt at different cooling rates using copper mold casting and melt spinning, respectively. Both the melt-spun ribbons and the cast cylinders display x-ray diffraction patterns without obvious crystalline peaks. However, the ribbons show soft magnetic properties, the cylinders are hard magnetic, and the crystallized alloys are not ferromagnetic at all. On the other hand, the cylinders show different exothermic transformation behavior than the ribbons upon heating to elevated temperatures. While the ribbons are regarded as amorphous, the structure of the cylinders prepared at slower cooling rate is considered to consist of metastable ordered clusters. This structure forms in the undercooled melt most likely due to intensive generation of ordered nuclei and slow growth kinetics. The magnetic coherence length, which is equivalent to the dimension of the ordered clusters, may be larger than the exchange length. Therefore, the cylinders shows much larger coercivity than the ribbons.

The unsolved question of the location of the gallium atoms within the structure is addressed. We have performed a high-resolution neutron diffraction investigation on powder samples evidencing a preferential substitution of Ga in the and sites of the structure. The crystal structure has been investigated using the Rietveld method and the evolution of the shorter iron–iron interatomic distances has been linked to the observed increase of the Curie temperature when the Ga concentration increases. The combined use of neutron diffraction investigation and of scanning electron microscope analysis reveals that the solubility limit of Ga is equal to 1.8 atoms per formula unit. The effects of Ga for Fe substitution on the structural and magnetic properties of the compounds have been studied. The magnetic moment values of each atom and the saturation magnetization are clearly sensitive to the Ga for Fe substitution but also to the temperature. A significant modification of the Nd atoms near neighborhood is observed via the evolution of the interatomic distances and the influence of the Ga concentration on the spin reorientation temperature is discussed. The angle of tilt of the magnetization away from the c axis has been determined below the spin reorientation temperature for both and phases. Finally, a comparison with the influence of Ga on the structural properties of compounds is presented.

A study of the spatially resolved water-occupied pore size distribution in a drying concrete cylinder is reported. Pore sizes are obtained from freezing point depression of pore water for a temperature range of 0 to −40 °C, assuming that the freezing point is inversely proportional to pore diameter. Single-point magnetic resonance imaging techniques were used to monitor unfrozen water content as functions of position and temperature. It was observed that freezing began at −10 °C in the cylinder center, which had the highest moisture content, and with a further temperature decrease, the freezing region gradually spread to the exposed end surfaces. The central region had a broad water-occupied pore size distribution, with pore diameters as large as 10 nm. The occupied pore sizes became progressively smaller as the moisture content decreased in proximity to the exposed surfaces.